Collaborative Research: Visible-Light-Augmented Reverse Water Gas Shift Reaction on Hybrid Plasmonic Photocatalysts

Photocatalysis is an attractive technology for the sustainable, solar-driven chemical conversion of greenhouse gases, such as carbon dioxide, to value-added fuels and chemicals. To this end, the project explores the selective photocatalytic reduction of carbon dioxide by hydrogen into carbon monoxide and water. This reaction is also known as the reverse water-gas shift reaction (RWGS).

The carbon monoxide product can be further transformed into a range of high-value chemicals and fuels. Among the earth-abundant metal and metal oxide materials that can serve as a catalyst for this reaction, copper-based nanocatalysts have emerged as one of the best candidates for the RWGS reaction. However, under conventional thermal energy-driven catalytic conditions, the copper nanocatalysts require relatively high operating reaction temperatures and suffer from less than desirable product selectivity.

This research project aims to develop a novel photocatalytic approach to achieving superior catalytic activity and desired-product selectivity for the RWGS reaction. The project also demonstrates sustainable energy concepts to local elementary and high school students through various outreach activities, including Chemkidz events at schools across Oklahoma, Summer Science Camp in Appalachia (West Virginia), and National Lab Day events at the Oklahoma State University and West Virginia University campuses.

In conventional catalytic processes, the dissipation of thermal energy drives the transformation of reactants on the surface of catalysts toward a variety of products. Challenges remain, however, for designing catalysts that can drive the breakage and formation of specific chemical bonds toward desirable products with the utmost selectivity. This research project develops a hybrid plasmonic photocatalytic approach for this purpose.

Hybrid plasmonic photocatalysts consist of light-absorbing plasmonic metals surrounded by catalytic metals or metal oxides. The hybrid plasmonic photocatalytic approach offers a unique opportunity to control catalytic activity and selectivity using photon stimuli as an additional degree of freedom. In hybrid plasmonic photocatalysts, such as Cu core/Cu2O shell, the electron transfer from the Cu core to the Cu2O shell can occur by Landau damping-mediated hot-electron-transfer pathway or by chemical interface damping (CID).

Although a fundamental understanding of the Landau damping-mediated hot-electron-transfer pathway is well established, design rules for the chemical interface damping pathway remain unknown. This collaborative project will develop design rules for chemical interface damping-induced electron-driven photochemistry. These rules will then be applied to the design of core/shell, Cu/Cu2O and Ag/Cu2O photocatalysts for the RWGS reaction.

This research project also aims to distinguish the role of chemical interface damping- and Landau damping-mediated electron-transfer pathways in hybrid plasmonic photocatalysts using photocatalytic rate and quantum efficiency measurements and in-situ femtosecond transient-absorption spectroscopy. It is hypothesized that the chemical interface damping pathway will exhibit higher quantum efficiency and minimal local heating effects compared to the Landau damping pathway.

Also, beyond the focus on Cu/Cu2O and Ag/Cu2O core/shell photocatalysts for the RWGS reaction, the design rules developed in this project can be applied to a wide range of other hybrid plasmonic nanostructures for photocatalytic and photovoltaic applications.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.